CORRELATION OF MICROSTRUCTURE AND PHOTOLUMINESCENCE FOR NANOMETER-SIZED SI CRYSTALS FORMED IN AN AMORPHOUS SIO2 MATRIX BY ION-IMPLANTATION

We have investigated microstructure and optical properties of thermal oxide films grown on crystalline Si wafer, modified by 1 MeVSi(+)-implantation and subsequent annealing at 1100 degrees C to segregate Si nanocrystals in an amorphous SiO2 matrix. Transmission electron microscopy indicates the formation of Si nanocrystals near the range of implanted Si ions in SiO2 after annealing and the growth in average size of Si crystals with increasing annealing time. Photoluminescence spectroscopy indicates that the luminescence intensity grows and then decreases as the annealing time increases, without changing the shape of the luminescence spectra. These results indicate that the photons are absorbed by Si nanocrystals with modified band-gap governed by the quantum confinement effects, and the emission of photons is nor due to direct electron-hole recombination inside Si nanocrystals, but is related to defects,probably at the interface between Si nanocrystals and SiO2.